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Homework Help: Science: Chemistry

Recent Homework Questions About Chemistry

Chemistry
Calcium chloride, CaCl2, is used in “hot packs”. When the solid is mixed with water, the products are favored. Based on this information, which of the following is true for the values of ΔH and ΔS for the dissolving process? CaCl2 (s) → Ca2+ (aq) + 2 Cl&#...

Chemistry
Ammonium nitrate, NH4NO3, is used in “cold packs”. Which statement best describes why the products are favored, when the solid is mixed with water? NH4NO3(s) → NH4+ (aq) + NO3- (aq) A) Heat is transferred to the surroundings to lower the temperature and the entropy ...

Science,chemistry
How do I write a balanced half ionic equation of aluminium oxide at the cathode?

AP Chemistry
Sodium can be extracted by heating naturally occurring salt until it is molten. An electrochemical process is then used to extract the sodium. Cl2 is produced at the anode, and Na is collected at the cathode. 1. Write the half-reactions that occur at the anode and the cathode...

Chemistry
When excited electron of phosphorus goes in d orbital from p orbital then particularly in which orbital of d (5 coz there are 5 suborbitals in d) that electron goes? And why?

Chemistry
Cobalt metal is added to steel to improve its resistance to corrosion.Calculate no. of moles in a cobalt contain 5×10^20

Chemistry
what are dipoles?

Chemistry
Is the atomic mass or atomic weight on the periodic table written in grams.

Chemistry
To what volume should 10L of 0.5M CH3COOH (Ka = 1.8×10–5) be diluted in order to double the OH– concentration?

Chemistry
Consider the following reactants. Which produces a gas? 1. NH4Cl(aq) + AgNO3(aq) → 2. Na2CO3(aq) + BaCl2(aq) → 3. Na2S(aq) + HCl(aq) → 4. All of these would produce a gas.

Chemistry
Does helium have an ionic radius? I searched and looked in an old Chem book, and come up empty. Hydrogen is not listed either. Is there a specific reason for this? Thank you.

Chemistry
What is the molar volume of pure water at 22 degrees Celsius?

Chemistry
Identify the precipitate(s) of the reaction that occurs when a silver nitrate solution is mixed with a sodium chloride solution. Check all that apply. silver nitrate sodium chloride sodium nitrate silver chloride

CHEMISTRY PLS HELP
If a sample of red blood cells at an osmotic pressure of 7.70 atm is placed in a solution that contains 0.050M calcium chloride (CaCl2) at 25°C, what is the freezing point of this solution if the density of the solution is 1.50 g/mL

Chemistry
If 0.0365 mol of CaCl2 is dissolved in water to make a 0.640 M solution, what is the volume of the solution?

Chemistry
1) 2 kg of solid copper is at its melting point. How much energy does it take to melt all the copper? Heat of fusion: 134 J/g Heat of Vaporization 5060 J/g q= mHf I know the equation but I do not understand know if this is correct. 2kg= 2000 grams q=(2000g) (134J/g) q=(2000) (...

Chemistry
Calculate normality of 27% H2SO4

Chemistry
In the titration of a solution of a weak acid HA with NaOH the pH is 5.0 after 10ml of NaOH solution has been added and 5.6 after 20ml of the NaOH solution has been added. Find the PKa of HA? Pls give some hints to solve this question...

chemistry
What is the composition of a methanol () – propanol () solution that has a vapor pressure of 121 torr at 40°C? At 40°C, the vapor pressures of pure methanol and pure propanol are 303 and 44.6 torr, respectively. Assume the solution is ideal. Mole fraction of methanol = ...

chemistry
Pentane (C5H12) and hexane (C6H14) form an ideal solution. At 25oC the vapor pressures of pentane and hexane are 511 and 150 torr, respectively. A solution is prepared by mixing 25 mL pentane (density, 0.63 g/mL) with 45 mL hexane (density, 0.66 g/mL). What is the vapor ...

chemistry
A solution is made by dissolving 22.9 g urea (), a nonelectrolyte, in 302 g water. (The vapor pressure of pure water is 23.8 torr at 25°C and 71.9 torr at 45°C.) Calculate the vapor pressure of this solution at 25°C. Vapor pressure = torr Calculate the vapor pressure of ...

chemistry
The normal boiling point of methanol is 64.7oC. A solution containing a nonvolatile solute dissolved in methanol has a vapor pressure of 670.0 torr at 64.7oC. What is the mole fraction of methanol in this solution?

chemistry
Glycerin, C3H8O3, is a nonvolatile liquid. What is the vapor pressure of a solution made by adding 159 g glycerin to 338 mL H2O at 39.8oC? The vapor pressure of pure water at 39.8oC is 54.74 torr and its density is 0.992 g/cm3.

chemistry
Calculate the solubility of in water at a partial pressure of of 140. torr at 25°C. The Henry's law constant for is for Henry's law in the form C = kP, where C is the gas concentration (mol/L).

chemistry
What mass of glycerin (), a nonelectrolyte, must be dissolved in 200.0 g water to give a solution with a freezing point of –0.900°C?

chemistry
The weight of a china dish with a saturated solution of sodium nitrate at 40°C is 80 g. After evaporating the whole solution the dish's weight along with the crystals is 40 g and solubility of NaNO3 at 40°C is 20 g. What is the weight of empty china dish ?

Chemistry
15.00g of ammonium nitrate decomposes into an expandable container acoording to the following equation. 2NH4NO3 ==> 2N2 g + 4H2O g + O2 g which has the highest partial pressure a. N2 b. H2O c. O2 i am not sure how to approach this problem. is there a simple way to solve ...

Chemistry
Classify the following reactions as precipitation reactions, oxidation-reduction reactions, or acid-base reactions. 1)2NaCl(aq)+K2H2Sb2O7(aq)==Na2H2SbO7(s)+​2KCl(aq) 2)(CH3COO)2Cu(aq)+(NH4)2C2O4(aq)==CuC2O4​(s)+2CH3COONH4(aq) 3)4Al(s)+3O2(g)==2Al2O3(s) 4)2Zn(s)+O2(...

Chemistry
When methane are burned in a bomb calorimeter the temperature rises from 21.00℃ to 25.18℃. The heat capacity of methane is 3.754x10^3 J/℃. The amount of heat, q (in kJ) absorbed by the calorimeter apparatus is: Correct Answer: 18.68 kJ My Work and my answer: ...

Chemistry
B2O3(s) + 3C(s) + 3Cl2 (g) ---> 2 BCl3(g) + 3CO(g) How many moles of chlorine are used up in a reaction that produced 0.35 kg of BCl3 I do not understand please help

Chemistry
2NO(g) + O2 (g) --> 2NO2 How many grams of NO are required to react fully with 5.00 mol of O2? I do not understand any of this please help

chemistry
WHAT does it mean for a phase of matter to have a definite shape and volume

Chemistry
The following replicate values were reported for the concentration of magnesium chloride, MgCl2, in mol/L. What value should be reported as the mean concentration of the chloride ion, Cl-, converted to ppm? (You may use the simplified definition of ppm.) 0.00141, 0.00138, 0....

chemistry
A metal bar having a mass of 212 g is heated to 125.0 C and then dropped into 375 g of water at 24.0 C. After a while the temp of the water and the metal is 34.2 C. If the specific heat of the metal is 0.831 J/g C, how much heat did the metal lose? How much heat did the water ...

Chemistry
How many grams of solid KOH must be added to 100ml of a buffer solution which is 0.1M each with respect to the weak acid HA and its potassium salt KA in order to make the pH of the solution 6.0?

chemistry
Write the balanced chemical equation for the oxidation of catechol to quinone.

Chemistry
Identify the oxidation-reduction reactions among the following: 1. Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s) 2. 2Na(s) + Cl2(aq) → 2NaCl(s) 3. 2Mg(s) + O2(g) → 2MgO Identify the oxidation-reduction reactions among the following: 1 and 2 only 2 and 3 only 1 and 3 ...

Chemistry
1.025g of an impure sample of a weak acid HX(mol mass = 82) is dissolved in 60ml of water and titrated with 0.25M NaOH. When half of the acid was neutralized the pH was found to be 5.0 and at the equivalence point the pH is 9.0. Find the % purity of this sample of HX Pls help...

Chemistry
0.299 g of NH4Cl is dissolved in 50.0 ml then titrated against 0.205 M NaOH. Calculate the pH at the equivalent point

Chemistry
Base = NaOH, 0.084 M drips 2ml at a time Acid = Phenol, KA=1.3*10^-10 You have 28.0 ml in flask, and it is 0.06 M How would you find the molarity and moles of OC6H5-1

Chemistry
Calculate the value of Z and its absolute standard deviation. All standard deviations shown are absolute. Show your work and report the standard deviation in the result with two significant digits (to confirm the correct result). Z = (1.18+/-0.07)x((2.21+/-0.05)^3)

Chemistry
What two facts did Newton need to be able to calculate the acceleration of the Moon?

Science (Chemistry) (Measurement Uncertainty)
Three students are asked to determine the mass of a coon. They each measure different values for the mass of the coin using a balance. Student A recorded a mass of 63.08g, student B recorded a mass of 63.022g and student C recorded a mass of 63.0328g. If the balance is ...

Chemistry
A beaker of nitric acid is neutralized with calcium hydroxide. Write a balanced molecular equation and a net ionic equation for his reaction

Chemistry
What effect does the presence of an impurity have on the freezing point of a liquid?

Chemistry Lab
Number of moles of HCl and Na2CO3 (show calculations) when 0.015 g of Na2CO3. How can I calculate this problem if I am only given the 0.015 grams of Na2CO3?

CHEMISTRY
15.0g of KCLO3 was crushed and heated with about 0.1g of MnO2.Write an equation for the reaction.

Chemistry
When an electric current passes through water during the process of electrolysis, two gases are formed. One gas has a boiling point of -183 C and the other has a boiling point of -253 C. Has a physical change or chemical change occurred? Explain. I think it is a chemical ...

Chemistry
Write the formulas of the compounds formed by NH4+ with the following anions: NO3−, HCO3−, SO42−, HPO42−. Express your answers as chemical formulas separated by commas. Use the given order of anions.

chemistry
what is the pH of a solution prepared by adding 0.65mol of LiOH(aq) to 1.0L of 0.30mol/L HNO3(aq)>

Chemistry
A student does a standard addition experiment by pipetting 25 mL of unknown, adding ferrous ion spikes and reagents, into a 100 mL volumetric flask and making up to the mark. The equation of the line has a slope of 0.103 and an intercept of 0.135 when the unit of concentration...

Chemistry
Each increase in pressure of 100 atm decreases the melting point of ice by about 1.0¡ÆC. Q. One possible explanation of why a skate moves smoothly over ice is that the pressure exerted by the skater on the ice lowers its freezing point and causes it to melt. The pressure ...

Chemistry
An Unknown Compound (M=60.09 g/mol) is composed of Carbon, Hydrogen and Oxygen. Combustion of 0.255 g of the unknown compound produces 0.561 g Carbon Dioxide and 0.306 g of Water. Determine the molecular formula of the compound.

General Chemistry
A typical human adults exhales 500 mL of air per breath. At this rate, calculate the volume of air exhaled after 20 breaths in units of cubic meters.

Chemistry
Calculate the amount of energy released in the formation of one mole of MgSe bonds (not lattice energy). The radius of the magnesium ion is 0.65 Å, and the radius of the selenide ion is 1.98 Å. Note that 1Å=10^−10m. I know I need to use the formula E=k(q1*q2)/d ...

Chemistry
What mass of Na2S is produced when 20g of sodium reacts with excess sulfur?

Chemistry
Ammonia (NH3) reacts with oxygen to produce nitric oxide (NO) and water (see balanced equation below). How many grams of oxygen do you need to react with 21.4 g ammonia? __4_NH3 + __5_O2 → __4_NO + _6__H2O

Chemistry
can you please please help me with these questions I don't know how to do any of them. I know how to calculate moles and grams and mole ratio,etc but I don't understand the limiting excess reactant and yield stuff. Thanks! 1.In the following chemical reaction, how many grams ...

Chemistry
To prepare a solution of NaCl, you weigh out 2.634 (0.002)g and dissolve it in a volumetric flask whose volume is 100.00 (0.08) mL. Express the molarity of the solution, along with its uncertainty.

Chemistry
can you please please help me with these questions I don't know how to do any of them. I know how to calculate moles and grams and mole ratio,etc but I don't understand the limiting excess reactant and yield stuff. Thanks! 1.In the following chemical reaction, how many grams ...

AP Chemistry
A 12.8 g sample of iron ore is treated as follows. The iron in the sample is all converted by a series of chemical reactions to Fe2O3. The mass of Fe2O3 is measured to be 21.3 g. What was the mass of iron in the sample of ore? Answer in units of g.

Chemistry
Identify the oxidation-reduction reactions among the following: 1. Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s) 2. 2Na(s) + Cl2(aq) → 2NaCl(s) 3. 2Mg(s) + O2(g) → 2MgO 1 and 2 only 2 and 3 only 1 and 3 only All of 1, 2, and 3 None of 1, 2, and 3

Chemistry
The mass of potassium iodate (KIO3) contained in an impure sample was determined by titration with sodium thiosulfate (0.1005 M). The impure KIO3 was dissolved in 50 cm 3 of water, an excess of potassium iodide (KI) and 5 cm^3 of dilute sulphuric acid was then added. At the ...

Chemistry
Prepare 30mL of a stock KI soln by mixing 10.0mL of the 0.03M KI in 0.2M KNO3 with 20.0mL of the .2M KNO3 Determine the concentration of the iodide ion. What does it mean by the 0.03M KI in 0.2M KNO3? Is this just bad wording of the question? Am I just mixing the 10.0mL of ....

Chemistry
A student prepares a soln that is initally 0.006M Pb2+ and 0.00450M I-. This soln is placed into a 1.00cm wide cuvet and inserted into the spectrometer producing as abosrbance reading of 0.430 at a wavelength of 456nm. What is the equilibrium concentration of the iodide ions ...

Chemistry
What specific evidence from the gold foil experiement led Rutherford to come to each of the following conclusions? The nucleus occupies very little space in the atom. Answer:He shot alpha particles through thin sheet of gold and discovered some were deflected An atom is made ...

chemistry
A 1.60 g sample of a mixture of naphthalene, C10H8, and anthracene, C14H10, is dissolved in 20.0 g benzene, C6H6. The freezing point of the solution is 2.81oC. What is the composition as mass percent of the sample mixture?

Chemistry
3. What experimental problems would confront you if you attempted to determine the concentration of the metal ions in solutions of each of the following reagents? a. Cr +3 which has a maximum absorbance at 407 nm with absorbtivity of 15 M -1 cm -1 and another at 574 nm with ...

chemistry
How can values of heats of formation found in tables be used to calculate heats of reactions? I am having a really hard time understanding this.

Chemistry
Calculate the amount of energy released in the formation of one mole of MgSe bonds (not lattice energy). The radius of the magnesium ion is 0.65 Å, and the radius of the selenide ion is 1.98 Å. Note that 1Å=10^−10m. I know I need to use the formula E=k(q1*q2)/d ...

chemistry
How much energy is required to make H2O(g) from H2O(l)? Basically this deals with bond energies and heats of formation. But I'm not sure how to find it

chemistry
What is n+1+m for 4p orbital and what is n+l+m for 4p orbital

chemistry
For a skydiver jumping out of a plane at an altitude of 1 km, what would be the concentration of oxygen in his (or her) blood knowing that air pressure at 1 km drops to 89,874 Pa? Assume ideal behavior of gases, normal breathing, 25 °C and constant air composition. Hint: ...

CHemistry
What is the molecular formula of glycerol (a compound containing C, H, and O) from the following combustion analysis: when 2.00 g glycerol are combusted, 2.865 g CO2 and 1.564 g H2O are recovered. I already found uts molar mass its 92g/mol

Analytical chemistry
A solution is created using 2.1700 grams of Calcium Hydroxide (MW is 74.093) in a 1L volumetric flask. A 50 mL aliquot is then taken and aded to a 350 mL volumteric flask and filled to the line. Finally, a 10 aliquot of the that solution is taken and added to a 100 mL ...

Analytical chemistry
0.6140 grams of sodium phosphate (Na3PO4) was dissolved in 2 L of water to make a stock solution. 34 mL of this solution is then diluted to 100mL volumetrically to prepare the final solution. Calculate the molarity of phosphate ions in this solution. Answer to 5 decimal places.

CHEMISTRY
calculate the weight of co2 by complete combustion of 1.5 \g of ethane

Chemistry
In a titration 100 mL of 3.65 g HCl is added to 200 mL of BA(oh)2 solution of an unknown concentration until the equivalent point find molarity of ba(oh)2

Chemistry
A handbook gives the heat of combustion of liquid carbon disulfide as -3.42 kcal/g of the liquid. Write the equation representing the combustion of 1 mol of carbon disufide and the accompanying ΔH value. (hint: the sulfur containing combustion product is sulfur dioxide).

Chemistry
Calculate the heat capacity of a sample of radiator coolant if a temperature rise from 5 to 107℃ requires 932 J of heat. My work: c=q/mΔT c=932J/(?)(107℃-5℃)

Chemistry
Tin and purple Iodine combine to form an orange solid tin iodide compound. If the compound contains 0.00383 moles of Sn and 0.01534 moles of I, what is its' empirical formula?

chemistry
I got this question wrong it was true/false the answer was false A supersaturated solution will have some solid undissolved in the bottom of the container. I don't know why its false?

Chemistry
I'm doing online homework and the follow question has come up: Write the formulas of the compounds formed by Pb4+ with the following anions: NO3−, ClO3−, SO32−, H2PO4−. Express your answers as chemical formulas separated by commas. Use the given order ...

chemistry
List the following strong electrolytes solutions in order of increasing boiling point. a. 0.1 M CaCl2 b. 0.1 M AlCl3 c. 0.1 M CaS

chemistry
 If we combine nitrous oxide (NO, laughing gas) with oxygen (O2) we produce nitrogen dioxide (NO2) according to the following reaction: 2NO + O2→ 2NO2 How many grams of NO2 will be produced when 5.00 moles of NO react?

chemistry
A solution containing 40 g of calcium bromide requires 14.2 g of chlorine to react completely with it and 22,2 g of calcium chloride is produced in addition to ehaever bromine is obtained. How many grams of calcium bromide are required to produce 10.0 pounds of bromine?

chemistry
Calculate the normality of solution containing 4g of sodium hydroxide present in 1 litre of solution ?

CHEMISTRY
I'm trying to figure out the percent composition of a mixture of an unknown (a combination of NaHCO3 and NaCl). Here's my data: Mass of 150mL of empty beaker: 80.937g Mass of 150mL beaker w/ unknown: 81.957g Mass of 150mL beaker w/ unknown after reaction: 89.126g Mass of ...

Chemistry
To clarify, a triple bond between carbon and oxygen is more stable than a triple bond between carbon and nitrogen because oxygen is more electronegative. Is my understanding correct?

chemistry
is heating iodine from its solid state to a liquid state a chemical or physical change?

chemistry
how many joules of heat are required to heat 149g of aluminum from 31.0 celcius to 75.5 celsius

Chemistry
I was given a solution of HCOOH with hand approximate concentration of 0.20 moles and I need to titrate this with a 0.110 V mol of NaOH. If I add 20 milliliters of hcooh to the beaker before I titrate approximately what volume of NaOH will be required to reach the endpoint?

Chemistry
Sample of 10.7g of O2 reacts completely with CO to form CO2 3a) How many grams of CO2 will be formed. So 10.7g (1mol/32g) (2molCO2/2molCO2)(22.01gCO2/1molCO2) = 14.7g. Please is this right 3b) is the mass of CO2 ypu determined in the equation (3a) the minimum or the maximum ...

Chemistry
74. Sodium hydrogen carbonate is also known as baking soda. When this compound is heated, it decomposes to sodium carbonate, carbon dioxide, and water vapor. Write the balanced equation for this reaction. What volume of carbon dioxide gas at 77 degrees C and 756 mmHg will be ...

Chemistry
Consider a mixture of two gases,A and B, confined in accosted vessel. A quantity of a third gas C, is added to the same vas sekar the same temperature. How does the addition of gas C affect the following: a. The partial pressure of gas A. b. The total pressure in the vassal, c...

Chemistry
You want to heat 1 kg of water 10 degrees celsius and you have the following methods under consideration. The heat capacity of water is 4.184 J/K g. (a) You can heat it with a mechanical eggbeater that is powered by a 1-kg mass on a rope over a pulley. How far does the mass ...

Chemistry
Which of the following compounds has an atom with an unfilled valence shell of electrons? A) H3O+ B) BF3 C) CH3OH D) NaI

Chemistry
Use bond energies to determine the energy transferred in the reaction between hydrogen and chlorine to make hydrogen chloride. H2 (g) + Cl2 (g) → 2HCl (g)

Chemistry
What volume of (2.5M) Hydrochloric Acid will be needed to neutralize 359mL of a 1.50M solution of potassium hydroxide?

Chemistry
How do you write the isotopic symbol for Uranium -238?

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